diff --git a/pkgs/development/ocaml-modules/fix/default.nix b/pkgs/development/ocaml-modules/fix/default.nix
index 1075e42aacc1..c2424072e74a 100644
--- a/pkgs/development/ocaml-modules/fix/default.nix
+++ b/pkgs/development/ocaml-modules/fix/default.nix
@@ -6,18 +6,17 @@
 
 buildDunePackage rec {
   pname = "fix";
-  version = "20250428";
+  version = "20250919";
 
   src = fetchFromGitLab {
     domain = "gitlab.inria.fr";
     owner = "fpottier";
     repo = "fix";
-    rev = version;
-    sha256 = "sha256-ZfIKx0BMhnmrqmfyqRi9ElZN1xdkupsDmfRg1GD3l/Q=";
+    tag = version;
+    hash = "sha256-CVxOLlSKKX1kb1bi6IbSo7SH5GsVynI4de0c5NUmq+s=";
   };
 
   minimalOCamlVersion = "4.03";
-  useDune2 = true;
 
   meta = with lib; {
     homepage = "https://gitlab.inria.fr/fpottier/fix/";